Improvement in fusible plugs for boilers



Nrrn STATES ArnNr muon.

JOHN SMITH, OF WEN'IWORTH ROAD, ENGLAND.

Specification forming part of Letters Patent No. 7,076, dated March 28,1865.

To all whom it may concern.-

Beit known that I, JOHN SMITH, of Edward Street, Wentworth Road, BowRoad, East, in the county of Middlesex, Kingdom of Great Britain,engineer, have invented certain new and useful Improvements in FusiblePlugs for Steam-Boilers; and I do hereby declare the following to be afull, clear, and exact descripticn of the same, reference being had tothe accompanying sheet of drawings, and to the letters of referencemarked thereon.

My invention consists of' improvements in fusible plugs made use of toprevent danger or injury to steam-boilers by deficiency of water. I formthe body of the plug (which has usually been made in one piece screweddirect into the crown of the boiler-furnace) in two parts, so that theone part containing the plug may at any time be removed withoutdisturbing the part which is screwed into the boiler. In some cases Imake these plugs to be inserted or fixed entirely from the inside of thefire-box or flue without the necessity of entering the boiler for thepurpose. I form that part of the plug which is intended to be blown outby the fusion of the soft holding metal and the hole in which it isplaced in such manner as to present a greatly-increased resistance tothe blowing out of the plug by pressure alone. I effect this either bycutting grooves or screw-threads in the hole and similar grooves orthreads in or upon the blowout piece and running the fusible metalbetween, so that the whole depth of the fusible metal must be shearedfor pressure alone to havethe effect referred to. Otherwise, instead ofturning grooves in or screwin gthe two parts, as described, I form eachof them with a recess so that the two, when placed together, will form acavity in which the fusible metal may be run, and which will effect asimilar object.

The following more full description will enable competent persons to.make and use my invention.

Figurel of the accompanying sheet of drawings is a vertical section of afusible plug constructed according tomy invention. In this case the plugis intended to be inserted from the flue or fire-box without thenecessity of entering the boiler for the purpose. rlhe part of the pluga, intended toube blown out, is in this instance united to the main bodyb of the plug by means of fusible metal run into a space, o, formed byturning a groove or recess in each of the parts a and b., The strengthof the plug to resist pressure alone is further increased bydiillingholes, as shown, through the two parts of the plug, so that thefusible metal may penetrate into and fill them.

Fig. 2 is a modification of the foregoing, in which screw-threads arecut in each of the parts a and b, and the fusible metal run betweenthein ln this, as in the former case, the strength of the fusible metalto resist pressure is increased by drilling holes through the two parts,as shown.

Fig. 3 represents a plug in which thc parts e and b are united, as inFig. l, but which is formed with an additional part, d,intcnded toremain screwed into the boiler, and being of brass or gun-metal tofacilitate the removal, when required, of thc parts united by thefusible metal.

Having now fully described and ascertained the nature of my saidinvention and the inanner in which the same may be performed, I wouldhave it understood that, without limiting myself to the precise detailsrepresented, I cla-im as my invention and desire to secure by LettersPatent- 1. The construction of fusible plugs with recesses or groovesfor the purpose of increasing the power of the fusible metal to resistshearing, substantially as described.

2. The construction of fusible plugs with an additional part which mayremain screwed into or otherwise attached to the boiler, when the partcontaining the fusible metal is removed, as described.

In witness whereof' I have signed my name to this specification in thepresence of two subscribing witnesses.

London, December 13, i864.

JOHN SMITH.

Vitnesses W. LLOYD Wiss,

Assoc. L. E., Chandos Ohamberc, Adelphi, London, IV. 0. GEORGE F.WARREN,

No. 17 Gracechtwch street, E. 0.,

London.

